1. Field of the Invention
The present invention relates to an industrial robot in which an umbilical-member connected to a work tool or a motor mounted on a rotatable wrist element is disposed to run along the wrist element from an arm to the tool or the motor.
2. Description of Related Art
When an industrial robot such as a welding robot, a handling robot, or the like, is used to perform welding operation or handling operation, filament bodies such as cables, pipelines, etc., for supplying gas or power, or transmitting signal to the work tool such as a welding torch or a hand mounted to the distal end of a wrist element are required. When these filament bodies are disposed along an arm of the robot or along a wrist element rotatably mounted to the arm, the filament bodies may give rise to interference with the arm or other peripheral equipments, or rotation of the arm or wrist element may produce tension in the filament bodies, resulting in breakage or damage of the filament bodies. In order to eliminate such inconveniences, several proposals have been made, including, for example, Japanese Patent Publication No. 2005-96073 and Japanese Patent Publication No. 2004-90135, which disclose insertion of filament bodies inside the arm or wrist element.
Japanese Patent Publication No. 2005-96073 discloses a processing structure for disposing an umbilical-member, in which, between a wire supply apparatus mounted on an arm and a work tool, the umbilical-member supplied from the wire supply apparatus to the work tool is passed inside the arm and is drawn out from a passing port opened at a trunk portion of the wrist element, and is disposed to run along the wrist element so as to be connected to a welding torch. Within the arm, a motor for driving the wrist, a reduction gear and an intermediate shaft are arranged in a row coaxial with the rotation axis of the wrist element. The umbilical-member is inserted into the hollow cylindrical portion of the intermediate shaft, and is drawn out of the passing port.
Japanese Patent Publication No. 2004-90135 discloses a processing structure for disposing filament bodies in a joint section having one arm rotatably connected to the other arm (wrist element), in which the filament bodies are disposed inside the two arms. A motor and a reduction gear are incorporated in the one arm coaxially with the rotation axis of the other arm. Output shaft of the reduction gear extends into the other arm, and is connected via a linkage plate to the other arm. A flexible tube as an air supply pipe is loosely wound around the outer circumference of the output shaft. Further outside of the flexible tube, a flat cable is wound around via a cylindrical partition plate.
In the method disclosed in Japanese Patent Publication No. 2004-90135, when one arm is rotated in one direction relative to the other arm, the flexible tube and the flat cable are displaced so as to tighten the winding. On the contrary, when one arm is rotated in the opposite direction relative to the other arm, the flexible tube and the flat cable are displaced so as to relax the winding. Thus, the flexible tube and the flat cable permit the rotation range of the arm to be increased without giving rise to twisting or tension in the filament bodies.
Thus, the above-described Japanese Patent Publication No. 2005-96073 and Japanese Patent Publication No. 2004-90135 provide the processing structure for disposing filament bodies, in which filament bodies are passed through the inside of the forearm and are connected to the wire supply apparatus or the work tool. Further, Japanese Patent Publication No. 2004-90135 discloses a processing structure in which a flexible tube and a flat cable are disposed separately in the inner space of one arm. In accordance with the present invention, such a processing structure stabilizes the behavior of the flexible tube and the flat cable, and thereby increases the reliability of connection. However, it is required to achieve a more compact and light-weight arm having a reduction gear incorporated therein in order to further stabilize the behavior of the arm and wrist element of a robot. Thus, although there is still a need for size reduction, there is a limit to size reduction in prior art.
Thus, in the method disclosed in Japanese Patent Publication No. 2005-96073, for example, there is a problem that the wire supply apparatus projects behind the arm. In the method disclosed in Japanese Patent Publication No. 2004-90135, there is a problem that, although a flat cable is used in order to reduce the processing space for the cable, the motor and the reduction gear are arranged in a row coinciding with the rotation axis of the other arm, and therefore, one arm cannot be formed compact in axial direction and the benefit of the flat cable cannot be fully utilized.